The word 从天而降 is formed by sequentially combining the character 从 (meaning 'from'), 天 (meaning 'sky' or 'heaven'), 而 (a conjunctive particle used to link actions, here indicating 'and then' or 'thus'), and 降 (meaning 'to descend' or 'to fall'), resulting in a literal sense of 'descend from the sky' to express something occurring suddenly or unexpectedly.